Grade 10 Academic Science - Chemistry
Types of Reactions
There are several types of chemical reactions
1. combustion
2. synthesis reactions
3. decomposition reactions
4. displacement reactions
Combustion
This is a reaction where a substance reacts with oxygen to produce something called an oxide.
Oxides are compounds that contain oxygen. The reaction usually releases heat in the form of
heat and/or light.
An example is a lighter
butane + oxygen  carbon dioxide + water + energy
C4H10 + O2  CO2 + H2O
NOTE: You must BALANCE this equation (i.e., number of reactants must equal number of
products
2C4H10 + 13O2  8CO2 + 10H2O
* If there is not enough oxygen available, CO (carbon monoxide) is produced which is dangerous
to humans.*
Synthesis Reactions
During a synthesis reaction, two things attach to make one new substance:
A + B  AB
An example is placing a magnesium ribbon in Bunsen burner flame
magnesium + oxygen  magnesium oxide
Mg + O2  MgO
Again, balance the chemical equation
2Mg + O2  2 MgO
Decomposition Reactions
During decomposition reactions, a larger compound is broken down:
AB  A + B
The example is electrolysis of water with splint tests of gases
water  oxygen gas + hydrogen gas
2H2O  O2 + 2H2
Displacement Reactions
In a displacement reaction, elements trade places and recombine. There are two kinds of
displacement reactions:
Single Displacement Reactions
In this kind of reaction an element will displace another element from a
compound:
A + BC  B + AC
This reaction can be demonstrated by combining magnesium + silver nitrate 
silver + magnesium nitrate
Mg + 2AgNO3  2Ag + Mg(NO3)2

the magnesium displaces (takes the place of) the silver
Another example is bromine + calcium iodide  iodine + calcium bromide
Br2 + CaI2  I2 + CaBr2
NOTE: metals displace metals / non-metals displace non-metals
Double Displacement Reactions
In a double displacement reaction two compounds are mixed and the metals
switch places:
AB + CD  AD + CB
A demonstration is lead (II) nitrate + potassium iodide  lead (II) iodide +
potassium nitrate
Pb(NO3)2 + 2KI  PbI2 + 2KNO3